Hriston
Dungeon Master of Middle-earth (He/him)
I was with you up til here.
If 'surprise' was caused by the 'revelation' of a previously unknown creature, this would mean that it's impossible to Assassinate a creature that cannot sense you. That having something with fantasy leprousy (so cannot feel anything) is immune to auto-crits while he is asleep!
Not true! An attack from hiding unequivocally reveals your position when it hits or misses. Creatures know when they are being attacked. If they don't they have worse problems than being surprised.
Next, if the target was surprised because he didn't notice the threat at the beginning of combat, how will he suddenly not be surprised any more at a certain point in round one if nothing that he knows about has changed? If the target rolled a higher initiative, his turn occurs before the assassin actually does anything. If surprise is 'caused' by the 'revelation' of something unexpected, how can his state of being surprised end before something unexpected happens?
All turns in the round are simultaneous. If the target has the higher initiative that means his turn is resolved before the assassin's. It does not mean that the assassin does not begin attacking until after the target's turn is over. Just that the attack doesn't hit until after the target's turn is over.